1. Field of the Invention
This invention relates generally to gaseous discharge lamps and, more particularly, to a circuit and apparatus which provide high voltage pulses for starting high pressure sodium discharge lamps.
2. Description of the Prior Art
Starting circuits and apparatus for high pressure sodium lamps are well known in the art. Examples of such circuits and apparatus are disclosed in U.S. Pat. Nos. 4,322,660 to Johnson, 4,143,304 to Hitchcock, and 4,072,878 to Engel, et al.
The Johnson patent discloses an apparatus for providing high voltage pulses for starting a high pressure sodium discharge lamp, said apparatus having a single capacitor in series with a blocking diode and a charging resistor. When the voltage of the capacitor reaches a predetermined voltage exceeding the zener voltage of a parallel zener diode, the capacitor discharges through a ballast which is connected in autotransformer relationship therewith to provide the high voltage pulse to start the lamp.
The Hitchcock patent discloses an apparatus using a voltage amplification circuit the output of which is applied across a ballast reactor which is connected thereto in autotransformer relationship.
The Engel, et al. patent discloses an apparatus that provides for high voltage pulses for starting a sodium discharge lamp by using the breakdown characteristics of a zener diode to provide timed starting pulses.